/*-------------------------------------------------------------------------
 *
 * rewriteSupport.c
 *
 *
 * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *      src/backend/rewrite/rewriteSupport.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/heapam.h"
#include "access/htup_details.h"
#include "catalog/indexing.h"
#include "catalog/pg_rewrite.h"
#include "rewrite/rewriteSupport.h"
#include "utils/fmgroids.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
#include "utils/syscache.h"
#include "utils/tqual.h"


/*
 * Is there a rule by the given name?
 */
bool
IsDefinedRewriteRule(Oid owningRel, const char *ruleName)
{
    return SearchSysCacheExists2(RULERELNAME,
                                 ObjectIdGetDatum(owningRel),
                                 PointerGetDatum(ruleName));
}


/*
 * SetRelationRuleStatus
 *        Set the value of the relation's relhasrules field in pg_class.
 *
 * NOTE: caller must be holding an appropriate lock on the relation.
 *
 * NOTE: an important side-effect of this operation is that an SI invalidation
 * message is sent out to all backends --- including me --- causing relcache
 * entries to be flushed or updated with the new set of rules for the table.
 * This must happen even if we find that no change is needed in the pg_class
 * row.
 */
void
SetRelationRuleStatus(Oid relationId, bool relHasRules)
{
    Relation    relationRelation;
    HeapTuple    tuple;
    Form_pg_class classForm;

    /*
     * Find the tuple to update in pg_class, using syscache for the lookup.
     */
    relationRelation = heap_open(RelationRelationId, RowExclusiveLock);
    tuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relationId));
    if (!HeapTupleIsValid(tuple))
        elog(ERROR, "cache lookup failed for relation %u", relationId);
    classForm = (Form_pg_class) GETSTRUCT(tuple);

    if (classForm->relhasrules != relHasRules)
    {
        /* Do the update */
        classForm->relhasrules = relHasRules;

        CatalogTupleUpdate(relationRelation, &tuple->t_self, tuple);
    }
    else
    {
        /* no need to change tuple, but force relcache rebuild anyway */
        CacheInvalidateRelcacheByTuple(tuple);
    }

    heap_freetuple(tuple);
    heap_close(relationRelation, RowExclusiveLock);
}

/*
 * Find rule oid.
 *
 * If missing_ok is false, throw an error if rule name not found.  If
 * true, just return InvalidOid.
 */
Oid
get_rewrite_oid(Oid relid, const char *rulename, bool missing_ok)
{
    HeapTuple    tuple;
    Oid            ruleoid;

    /* Find the rule's pg_rewrite tuple, get its OID */
    tuple = SearchSysCache2(RULERELNAME,
                            ObjectIdGetDatum(relid),
                            PointerGetDatum(rulename));
    if (!HeapTupleIsValid(tuple))
    {
        if (missing_ok)
            return InvalidOid;
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_OBJECT),
                 errmsg("rule \"%s\" for relation \"%s\" does not exist",
                        rulename, get_rel_name(relid))));
    }
    Assert(relid == ((Form_pg_rewrite) GETSTRUCT(tuple))->ev_class);
    ruleoid = HeapTupleGetOid(tuple);
    ReleaseSysCache(tuple);
    return ruleoid;
}
